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"  They  not  only  work  for  nothing  and  board  themselves,  but  they  pay  for  the 
privilege."— Davenport. 


UNIVERSITY  OF  ILLINOIS 


URBANA,  JULY,   1902. 


BULLETIN  NO.  76. 


ALFALFA  ON    ILLINOIS  SOIL. 


By   CYRIL   GEORGE    HOPKINS,   PH.  D.,    PROFESSOR   OF   AGRONOMY    IN   THE 

AGRICULTURAL  COLLEGE  AND  CHIEF  IN  AGRONOMY  AND  CHEMISTRY 

IN  THE  AGRICULTURAL  EXPERIMENT  STATION. 


Many  different  farmers  have  tried  to  grow  alfalfa  in  various 
sections  of  Illinois,  but,  in  most  cases,  it  has  been  pronounced  a 
failure.  Where  alfalfa  has  been  grown  with  success  in  Illinois,  it 
has  usually  been  necessary  to  sow  it  on  very  rich  ground  or  to  keep 
it  well  manured.  This  Experiment  Station  tried  to  grow  alfalfa 
on  Illinois  soil  several  years  ago,  but  the  result  was  a  failure,  and 
this  is  found  to  have  been  a  very  common  experience  among  Illi- 
nois farmers  who  have  tried  to  grow  this  crop.  The  usual  experi- 
ence has  been  that  the  seed  germinates  well,  a  good  stand  of  plants 
is  secured,  and,  for  a  year  or  two,  it  grows  about  as  well  as  it  is 
reported  to  do  where  alfalfa  is  a  successful  crop  ;  but,  after  two  or 
three  years,  it  weakens,  stops  its  vigorous  growth,  and  seems  ready 
to  die.  It  is  then  pronounced  a  failure  and  the  ground  is  plowed 
up  and  used  for  other  crops.  This  is  the  report  which  has  been 


312  BULLETIN   NO.   76.  \_Jufy, 

received  by  the  Experiment  Station  from  many  Illinois  farmers 
who  have  tried  growing-  alfalfa,  and  it  agrees  with  our  own  obser- 
vations in  a  great  majority  of  cases.  And  this  experience  is  com- 
mon not  in  Illinois  alone,  but  from  Indiana,  Ohio,  Michigan,  Wis- 
consin, and  Iowa  come  reports  of  similar  experiences. 

In  theory,  alfalfa  ought  to  grow  and  do  well  on  Illinois  soils, 
and  it  ought  not  to  require  heavy  and  frequent  applications  oi 
manures  ;  because  alfalfa  is  a  very  deep  rooting  crop  and  is  thus 
capable  of  drawing  upon  the  soil  to  great  depths  for  the  necessary 
mineral  elements  of  plant  food,  and,  being  a  leguminous  plant,  it 
has  the  power  of  "gathering"  nitrogen  from  the  inexhaustible 
supply  of  the  air,  by  means  of  the  bacteria  which  inhabit  its 
roots. 

Numerous  observations  made  on  several  fields  of  alfalfa  in  dif- 
ferent sections  of  the  State  during  the  past  few  years  led  me  to 
question  whether  alfalfa  has  the  power  to  secure  nitrogen  from 
the  atmosphere,  when  grown  on  Illinois  soil.  First,  because,  in 
nearly  every  field  examined,  the  plants  presented  the  same  peculiar 
appearance  which  plants  show  when  grown  under  artificial  condi- 
tions -with  an  insufficient  supply  of  nitrogen.  Second,  because,  in 
none  of  the  fields  where  alfalfa  presented  this  appearance  could 
there  be  found  any  tubercles,  or  nodules,  upon  the  roots  of  the 
alfalfa.  Third,  because  liberal  applications  of  barnyard  manure 
produced  a  vigorous  growth  and  a  natural  and  healthy  appearance. 

In  order  to  investigate  the  question,  why  Illinois  soil  does  not 
more  generally  produce  good  crops  of  alfalfa,  a  series  of  experi- 
ments was  begun  about  a  year  ago.  These  experiments  compre- 
hended the  application  of  various  elements  of  fertility  to  Illinois 
soil,  both  singly  and  in  combinations,  and  both  with  and  without 
the  inoculation  of  the  soil  with  the  alfalfa  bacteria  ;  that  is-  with 
the  bacteria  which  are  known  to  live  upon  the  alfalfa  root  in  other 
sections  of  the  country.  These  experiments  have  been  carried  on 
in  the  pot  culture  laboratory  under  controlled  conditions  and  also 
on  plots  of  ground  under  field  conditions. 

POT  CULTURE  EXPERIMENTS. 

The  pot  culture  experiments  were  planned  with  a  double  pur- 
pose, or  a  two-fold  object ;  first,  to  test  the  effect  of  applying  dif- 
ferent elements  of  plant  food  to  the  soil  to  determine  the  value  of 
such  applications  for  the  growing  of  alfalfa,  and,  second,  to  deter- 
mine the  effect  upon  the  growth  of  alfalfa  of  inoculating  the  soil 
with  the  bacteria  which  are  able  to  live  upon  the  roots  of  alfalfa 
and  gather  nitrogen  from  the  air  for  use  of  the  growing  alfalfa. 


IQ02.J  ALFALFA  ON  ILLINOIS  SOIL.  313 

APPLICATIONS  OF  DIFFERENT  ELEMENTS1  OF  PLANT  FOOD. 

These  pot  cultures  comprise  a  double  set  of  our  regular  series 
of  experiments  adopted  for  investigating1  soils  by  pot  cultures, 
which  is  as  follows  : 

Twelve  pots  are  all  filled  with  the  soil  to  be  investigated  and 
they  are  then  treated  with  the  following  applications  :8 

Pot  No.     1 — Check.     (Nothing  applied.) 

Pot  No.    2— Lime. 

Pot  No     3 — Lime  and  Nitrogen. 

Pot  No.    4 — Lime  and  Phosphorus. 

Pot  No.    5 — Lime  and  Potassium. 

Pot  No.    6 — Lime,  Nitrogen,  and  Phosphorus. 

Pot  No.    7  — Lime,  Nitrogen,  and  Potassium. 

Pot  No.    8 — Lime,  Phosphorus,  and  Potassium. 

Pot  No.    9 — Lime,  Nitrogen,  Phosphorus,  and  Potassium. 

Pot  No.  10 — Nitrogen,  Phosphorus,  and  Potassium. 

Pot  No.  11— Check. 

Pot  No.  12— Check. 

This  series  of  pot  cultures  shows  what  effect  is  produced  by 
applying  to  the  soil  any  of  the  three  different  important  elements 
of  fertility  or  any  possible  combination  of  them.  Lime  is  applied 
to  pots  3,  4,  5,  6,  7,  8,  and  9  to  correct  any  possible  acidity  and  in- 


1.  Among  the  ten  elements  of  plant  food  required  for  the  growth  of    all 
plants;  namely,  carbon,  oxygen,  hydrogen,  nitrogen,  phosphorus,  sulfur,   potas- 
sium, calcium,  magnesium,  and  iron,  the  three   elements,  nitrogen,   phosphorus 
and  potassium,  are  most  likely  to  be  deficient  in  the   soil.     Frequently  lime  (a 
compound  of  calcium  and  oxygen)  is  of  great  value   in  correcting  the  acidity  of 
sour  soils. 

2.  It  may  be  stated  that  the  elements  of  plant  food,  such  as  nitrogen,  phos- 
phorus, and  potassium,  may  be  applied  in  many  different  forms.     All  that  is  nec- 
essary is  that  the  plant  is  provided    with   the   element,  and  any   fertilizer  which 
will  furnish  the  element  in  an  available  form  is  satisfactory.     Thus,  the  element 
nitrogen  is  contained  in  sodium  nitrate,   in  potassium   nitrate,   in  ammonium  sul- 
fate,  and  ammonium  phosphate,  in  dried  blood,   in  ground   meat,  etc.,   etc.,  and 
any  one  of  those  substances  is   a  nitrogenous  fertilizer.     Likewise,  phosphorus 
may  be  applied  in  the  form  of  ammonium  phosphate  (which  is  both  nitrogenous 
and  phosphatic),  sodium  phosphate,  potassium  phosphate,  basic  phosphate,  bone 
phosphate,  etc.     Some  common  potassic  fertilizers  are  :     potassium  chlorid  (mu- 
riate of  potash  is  a  bad  name  for  the  same  salt ;  potassium  chlorid  tells  what  the 
substance  is  made  of  ;  namely,  potassium  and  chlorin),  potassium  sulfate,  potas- 
sium nitrate   (which  contains  both    potassium  and  nitrogen),  kainit,  etc.,  all  of 
which,  except  potassium  nitrate  (nitre),  are  obtained  from  the  mines  of  the  Kali 
Works  in  Germany.     In  this  connection,  it  may  be  noted  that  the  German  word 
Kali  is  from  the  Latin  Kalium  and  means  potassium,  and   the  symbol,  or  abbre- 
viation, "  K,"  is  used  for  this  element  among  all  the  civilized  nations. 


314  BULLETIN   NO.   76.  [July, 

sure  good  physical  condition.  If  the  soil  is  acid,  then  pot  4,  for 
example,  might  not  give  results  which  would  show  the  real  value 
or  need  of  an  application  of  phosphorus  to  the  soil,  although  a 
much  needed  application  had  been  made  of  the  element  phosphorus. 
It  will  be  observed  that  pot  No.  1  receives  no  special  treatment 
and,  of  course,  it  shows  what  the  ordinary  soil  does  with  no  appli- 
cation of  additional  elements  of  fertility.  The  first  ten  pots  really 
make  the  complete  series.  Pots  11  and  12  are  extras,  or  addi- 
tional checks. 

There  is  a  double  trial  as  to  the  value  of  an  application  of 
lime.  First,  by  comparison  between  1  and  2,  which  shows  the 
effect  of  applying  lime  alone.  Second,  by  comparison  between  ,9 
and  10,  which  shows  the  effect  of  applying  lime  after  insuring  a 
sufficent  supply  of  each  of  the  elements,  nitrogen,  phosphorus,  and 
potassium. 

Pots  3,  4,  and  5  will  show  the  effect  of  applying  to  the  soil, 
singly,  nitrogen,  phosphorus,  and  potassium,  respectively,  after  a 
sufficient  quantity  of  lime  has  been  added  to  neutralize  acidity. 

Pots  6,  7,  and  8  contain  all  possible  double  combinations  of 
those  three  elements,  and  by  comparing  pot  No.  6,  for  example, 
with  pots  3  and  4,  we  can  see,  first,  the  effect  of  applying  phos- 
phorus after  the  soil  has  been  well  supplied  with  nitrogen,  and, 
second,  the  effect  of  applying  nitrogen  after  sufficient  phosphorus 
has  been  insured.  Pot  No.  9  is  provided  with  an  abundance  of  all 
of  the  elements  of  fertility  and  a  comparison  of  the  results  from 
this  pot  with  those  from  6,  7,  and  8  will  show  the  effect  of  adding 
each  element  after  a  sufficient  supply  of  the  others  has  been  pro- 
vided. 

Attention  is  called  to  the  fact  that  this  system  really  includes 
five  separate  tests  for  each  of  the  three  elements,  nitrogen,  phos- 
phorus, and  potassium.  For  example,  if  nitrogen  is  the  only  ele- 
ment of  plant  food  which  a  soil  lacks  or  which  the  growing  plant 
is  unable  to  secure  from  the  soil  in  sufficient  quantity  for  maxi- 
mum development,  then  a  marked  effect  should  appear  in  all  of  the 
five  different  pots  to  which  nitrogen  is  applied ;  namely,  pots  3,  6, 
7,  9,  and  10. 

In  the  following  tables  and  in  the  photographs 

0  (zero)  means  no  fertilizer. 

L  means  Lime. 

N  means  Nitrogen. 

P  means  Phosphorus. 

K  means  Potassium  (Kalium) 


1902.]  ALFALFA  ON  ILLINOIS  SOIL.  315 

INOCULATION  WITH   ALFALFA   BACTERIA. 

As  stated  above,  two  series  of  pot  cultures  were  made  with 
alfalfa,  each  of  which  received  the  applications  of  the  different  ele- 
ments of  plant  food  as  described  above.  One  of  these  two  series 
of  twelve  pots  each  was  inoculated1  with  the  alfalfa  bacteria ,  the 
other  series  was  not.  In  all  other  respects  the  two  series  were 
treated  exactly  alike.  All  of  the  pots  were  filled  with  ordinary 
Illinois  black  prairie  soil,  and  25  alfalfa  seeds  were  planted  in 
each  pot.  They  were  kept  in  the  glass  house  and  were  watered 
with  very  clear  rain  water  which  was  practically  free  of  nitrogen, 
but  which  contained  a  trace  of  lime  dissolved  from  a  new  cistern  in 
which  it  was  stored. 

The  pots  were  all  planted  in  June,  1901.  The  seeds  germin- 
ated quite  well  and  a  fairly  uniform  stand  was  secured  in  all  of  the 
pots.  The  small  plants  grew  slowly  and  the  different  pots  showed 
no  very  marked  differences  for  several  months.  A  small  crop  was 
cut  from  all  the  pots  in  the  fall,  but  they  all  seemed  very  much 
alike  and  no  weights  of  the  cuttings  were  taken.  During  the  win- 
ter the  pots  showed  some  marked  differences  in  the  growth  of  the 
alfalfa  and  the  weights  of  the  cuttings  of  each  pot  were  taken  on 
March  14,  1902.  They  are  reported  in  the  tabular  statement. 

It  should  be  borne  in  mind  that  these  young  plants  were  not 
fully  developed  and  that  small  yields  of  alfalfa  were  to  be  expected, 
indeed  this  crop  from  the  pots  corresponds  to  the  second  clipping 
in  the  field,  which  is  usually  too  light  to  pay  for  the  trouble  of 
saving  it  for  hay,  and  consequently  it  is  usually  left  lying  on  the 
ground  after  the  mower.  For  yields2  of  the  more  fully  developed 
plants  see  Table  3. 


1.  The  inoculating  solution  was  made  by  shaking  500 grams  (about  I  pound) 
of  soil  (obtained  from  an  old  alfalfa  field  in  Kansas)  with  1,000  cc.  (about  I  quart) 
of  water,  and  allowing  it  to  settle.     One  cubic  centimeter  of  the  liquid  was  used 
for  each  alfalfa  seed  planted. 

2.  The  pots  used  were  10^  inches  in  diameter,  so  that  one  gram  of  produce 
per  pot   corresponds  to  one  pound  per  square   rod  or  to   160  pounds  per  acre 
(i  pound  =  453.6  grams).      While  the  exact  yield  per  pot  is  given  in  grams  in  the 
tabular  statement,  the  computed  rate  of  yield  in  pounds  per  acre  is  also  given 
and  this  rate  of  yield  is  used  in  the  discussion  in  the  text.     This  is  relatively  ac- 
curate and  it  is  used  because   we  are  accustomed  to  the  basis  of  pounds  per  acre. 
Another  advantage  is  that  the  results  from  the  pot  cultures  thus  become  more 
easily  comparable  with  the  actual  field  results   which  are  given  in  the  following 
pages. 


BULLETIN   NO.  76. 


TABLE  i.    ALFALFA  POT  CULTURES  ;  CUT  MARCH  14,  1902.    WEIGHTS  IN 
GRAMS  PER  POT  AND  POUNDS  PER  ACRE.' 


Serial  No.1 

Pot 

No. 

Treatment  applied 

Green  alfalfa 
(gms.  per  pot) 

Air-dry  hay 
(gms.  per  pot) 

Air-dry  hay 
(  Ib.  per  acre  ) 

i 
I 

2 
2 

3 

3 

4 
4 

5 
5 

6 
6 

7 
7 

8 
8 

9 

9 

10 
10 

ii 
ii 

12 
12 

25 
37 

26 
38 

27 
39 

28 
40 

29 
4i 

30 
42 

3i 
43 

32 
44 

33 
45 

34 

46 

35 
47 

36 
48 

0  :  

4 
9 

4 
8 

10 
14 

IO 

15 

9 

12 

18 
19 

17 
14 

10 

15 

16 
ii 

ii 

15 

7 

IO 

8 

12 

2 

3 

2 
2^ 

4 

5. 

3 

5 

2^ 
4 

6 

6 

5 

3 

5 

5 
4K 

4 
5 

2 

4 

3 
4 

320 
480 

320 
400 

640 
800 

480 
800 

400 
640 

II2O 
960 

960 
800 

480 
800 

800 
720 

640 
800 

320 
640 

480 
640 

0  :    Bacteria 
L:  

L  :  Bacteria 
LN:  

LN  :  Bacteria 
LP:   

LP  :  Bacteria 
LK  :  

LK  :  Bacteria 
LNP      

LNP     Bacteria 
LNK     

LNK     Bacteria 
LPK     

LPK     Bacteria 
LNPK  :  

LNPK  :  Bacteria 
NPK  :  

NPK  :  Bacteria 
0  :    

ii  :   Bacteria 

o  • 

0  :    Bacteria 

Two  facts  are  shown  very  distinctly  by  these  results  ;  first, 
that  the  addition  of  nitrogen  to  the  soil  increases  the  growth  of 
alfalfa  ;  and,  second,  that  the  inoculation  of  the  soil  with  the  proper 
bacteria  produces  a  similar  effect,  which  indicates  that  the  presence 
of  the  bacteria  enables  the  alfalfa  to  secure  a  supply  of  nitrogen 
from  the  air. 

The  average  yield  of  hay  per  acre  from  the  seven  uninoculated 
pots  receiving-  no  nitrog-en  is  400  pounds,  while  630  pounds  per  acre 
is  the  averag-e  yield  of  the  corresponding-  seven  inoculated  pots. 
Among  these  seven  pairs  of  pots  (1,  2,  4,  5/8,  11,  12)  the  inoculated 

i.  The  numbers  referred  to  in  the  discussion  are  the  duplicate  serial  num- 
bers, i  to  12,  but,  to  facilitate  reference  to  the  photographs,  the  tables  also  show 
the  individual  pot  numbers. 


I902.] 


ALFALFA  ON  ILLINOIS  SOIL. 


317 


pot  produced  a  larger  yield  in  every  instance,  and  in  several  cases 
the  inoculation  nearly  doubled  the  yield.  The  average  yield  per 
acre  of  five  uninoculated  pots  receiving1  nitrogen  (Series  3,  6,  7,  9, 
10)  was  830  pounds,  more  than  double  the  yield  of  the  uninoculated 
pots  receiving  no  nitrogen.  The  inoculation  of  pots  to  which  nitro- 
gen had  been  applied  produced  no  constant  effect,  which  indicates 
that,  the  bacteria  are  of  no  value  if  the  soil  is  abundantly  supplied 
with!  nitrogen.  In  fact,  under.this  condition  the  uninoculated  pots 
produced  a  slighly  higher  average  yield. 

It  may  be  of  interest  to  note  that  the  highest  yield  secured  from 
any  single  pot  was  1,120  pounds  per  acre  from  pot  30  in  series  6  to 
which  phosphorus  as  well  as  nitrogen  had  been  applied.  There  are 
some  other  results  which  indicate  that  an  application  of  phospho- 
rus to  the  soil  increases  the  growth  of  alfalfa. 

TABLE  2.    NOTES  ON  ALFALFA  POT  CULTURES  FROM  MARCH  14  TO  APRIL 

23,  1902. 


Serial 

No. 

Pot 

No. 

Treatment  applied 

Height  of  plants  (inches) 

Color 
of  foliage 

Mar.  26 

April  4 

April  12 

April  19 

i 
i 

2 

2 

3 
3 

4 
4 

5 

5 

6 
6 

7 
7 

8 
8 

9 
9 

10 

10 

ii 
ii 

12 
12 

25 
37 

26 
38 

27 
39 

,28 
40 

29 
41 

30 
42 

3i 
43 

32 
44 

33 
45 

3i 
46 

35 
47 

36 
48 

0:  

3 
3 

3^ 
M 

6 
6 

i- 

3 
5 

8 
8 

5 
5 

.   i 

6 

6/2 

6l/z 
6 

3 

4 

3 
4 

4 

5 

4 

5 

7 
7 

4 

7 

4 
6 

8 
8 

-     7 
7 

4 
8 

9 
9 

9 

9 

4 

5 

4 

5 

5 
7 

I 

1 
7 

5 

10 

4 
10 

12 
12 

9 
12 

4 
13 

12 
13 

12 
13 

I 

> 

5 
7 

5 
13 

5 
13 

8 
13 

5 
13 

5 
13 

13 
13 

13 
i3 

4 
15 

13 
15 

13 
15 

5 
13 

5 
13 

pale  green 
dark  green 

pale  green 
dark  green 

dark  green 
dark  green 

pale  green 
dark  green 

pale  green 
dark  green 

dark  green 
dark  green 

dark  green 
dark  green 

pale  green 
dark  green 

dark  green 
dark  green 

dark  green 
dark  green 

pale  green 
dark  green 

pale  green 
dark  green 

0  :   Bacteria 
L:    

L  :    Bacteria 
LN  :  

LN  :  Bacteria 
LP  :  

LP  :  Bacteria 
LK  :  

LK  :  Bacteria 
LNP:  

LNP  :  Bacteria 
LNK:  

LNK  :  Bacteria 
LPK:    

LPK  :  Bacteria 
LNPK  :  

LNPK  :  Bacteria 
NPK  :  

NPK  :  Bacteria 
0  :  

0  :  Bacteria 
0  :  

0  :  Bacteria 

BULLETIN   NO.   76. 


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ALFALFA  ON  ILLINOIS  SOIL. 


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320 


BULLETIN   NO.   76. 


[July, 


The  series  of  notes  in  Table  2  and  the  photographs  which  fol- 
low illustrate  the  growth  and  appearance  of  the  alfalfa  in  the  dif- 
ferent pots,  between  March  14  and  April  23.  Another  crop  was 
cut  from  all  of  the  pots  on  April  23  and  the  weights  of  the  alfalfa 
secured  from  each  pot  are  given  in  Table  3. 

TABLE  3.    ALFALFA  Pox  CULTURES  ;  CUT  APRIL  23,  1902.     WEIGHTS  IN  GRAMS 
PER  POT  AND  POUNDS  PER  ACRE. 


Serial  No. 

Pot 
No. 

Treatment  applied 

Green  alfalfa 
'gms.  per  pot) 

Air-dry  hay 
(gms.  per  pot) 

Air-dry  hay 
(Ib.    per  acre) 

I 

2? 

0:    

g 

2 

^20 

i 

2 

37 
->6 

0:    Bacteria 
L:  

37 

12 

9 
2 

1440 
320 

2 

T. 

38 
27 

L:  Bacteria 
LN:  

34 
38 

7 
9 

II2O 
I44O 

3 

4. 

39 
?8 

LN:  Bacteria 
LP:  

44 

7 

10 

i 

l6oo 
1  60 

4 

c 

40 

20 

LP:  Bacteria 
LK- 

44 

7 

10 
I 

l6oO 

160 

5 
6 

41 

3° 

LK:  Bacteria 
LNP:  

32 
66 

7 
16 

II2O 

2t;6o 

6 

7 

42 
^i 

LNP:  Bacteria 
LNK:  

79 

cc 

19 
n 

3040 
1760' 

7 
8 

43 
32 

LNK:  Bacteria 
LPK:  

59 
7 

13 
i 

2080 
160 

8 
o 

44 
33 

LPK:  Bacteria 
LNPK:  

67 
65 

17 
16 

2720 
2560 

9 
10 

45 
^4 

LNPK:  Bacteria 
NPK:    

85 
68 

22 

i6>£ 

3520 
2640 

10 

II 

f 
46 

^ 

NPK:   Bacteria 
o-                

IOO 
IO 

20 
2 

3200 
320 

II 

12 

47 
36 

0:   Bacteria 
0:    .'  

24 

IO 

5 
2 

800 
320 

12 

48 

o:  Bacteria 

34 

7 

II2O 

The  seven  uninoculated  pots  receiving  no  nitrogen  made  com- 
paratively  small  growth1  and  showed  uniformly  throughout    the 

i.  It  may  be  observed  that  the  uninoculated  pots  receiving  phosphorus  or 
potassium  or  both,  with  lime,  but  without  nitrogen,  (4,  5,  8)  yielded  even  less  than 
the  uninoculated  pots  which  received  lime  only  or  no  treatment  whatever  (i,  2, 
11,  12).  I  know  of  no  explanation  for  this  unless  it  be  found  in  the  fact  that  the 
yield  of  the  previous  crops  from  these  fertilized  pots  was  larger  than  from  the 
unfertilized  pots  and  the  supply  of  available  nitrogen  had  been  correspondingly 
reduced. 


1902.]  ALFALFA  ON  ILLINOIS  SOIL.  321 

period  of  nearly  six  weeks  the  characteristic  pale  yellowish  green 
color  indicative  of  an  insufficient  supply  of  nitrogen.  The  yields 
from  these  seven  pots  are  very  small,  in  no  case  exceeding-  the  rate 
of  320  pounds  per  acre,  while  1650  pounds  per  acre  is  the  average 
yield  of  the  corresponding-  inoculated  pots.  The  yield  from  the 
inoculated  pots  rang-es  from  2^£  to  17  times  the  yield  from  the 
uninoculated  pots.  For  example,  the  most  favored  pot  receiving 
,no  nitrog-en  (serial  No.  8),  to  which  applications  of  lime,  phos- 
phorus, and  potassium  were  made,  yielded,  when  uninoculated,  only 
160  pounds  of  hay  per  acre,  while  2,720  pounds  per  acre  was  the 
yield  of  the  corresponding-  inoculated  pot. 

The  crops  produced  on  the  seven  uninoculated  pots  receiving- 
no  nitrog-en  would  certainly  be  pronounced  a  failure,  but  the  in- 
oculated pots  which  produced  yields  from  ^  to  1^  tons  of  alfalfa 
hay  per  acre  in  less  than  six  weeks  from  the  previous  cutting-  give 
evidence  of  being-  a  very  decided  success,  considering-  that  this  is  the 
third  cutting-  and  corresponds  to  the  third  clipping-  in  the  field, 
which  is  frequently  too  light  to  pay  for  saving. 

EFFECT  OF  NITROGEN  AND  BACTERIA. 

The  applications  of  nitrogen  produced  a  very  marked  increase 
in  yields,  but  it  is  interesting  to  note  that  even  these  artificial  sup- 
plies of  nitrogen  had  evidently  become  somewhat  depleted  by  the 
removal  of  the  previous  crops  and  were  no  longer  sufficient  for  the 
greatest  possible  growth  of  the  alfalfa;  and,  consequently,  in  every 
case  where  pots  receiving  nitrogen  were  also  inoculated,  a  notable 
increase  in  growth  and  yield  occurred.  In  the  most  favored  pots 
(serial  No.  9),  to  which  lime,  phosphorus,  and  potassium  were  sup- 
plied with  the  nitrogen,  this  increased  yield  produced  by  the 
bacteria  amounted  to  nearly  one-half  ton  per  acre,  the  uninoculated 
pot  yielding  at  the  rate  of  2,560  pounds  per  acre,  while  3,520 
pounds  was  the  rate  of  yield  of  the  corresponding  inoculated  pot. 

Applications  of  phosphorus  or  potassium  without  bacteria  or 
nitrogen  (4,  5,  8)  are  of  no  value  to  the  alfalfa. 

EFFECT  OF  PHOSPHORUS. 

Phosphorus  applied  to  the  inoculated  pots  or  to  the  uninocu- 
lated pots  receiving  nitrogen  produced  a  very  marked  increase  in 
yield  in  every  instance.  These  results  confirm  the  indications  ob- 
served in  the  previous  crops  and  prove  conclusively  that,  after  pro- 
vision has  been  made  for  a  sufficient  supply  of  nitrogen,  applica- 
tions of  phosphorus  to  this  soil  were  greatly  to  the  advantage  of 
the  alfalfa  crop.  For  instance  where  lime  and  nitrogen  alone  were 


322  BULLETIN   NO.   76.  [July, 

applied  (3)  1,440  pounds  of  hay  per  acre  were  produced,  while 
2,560  pounds  was  the  rate  of  yield  where  phosphorus  was  added 
(6).  The  treatment :  lime,  nitrog-en,  bacteria  (3)  produced  a 
yield  of  1,600  pounds,  which  was  increased  to  3,040  pounds  by  the 
addition  of  phosphorus  (6).  Under  the  most  favorable  conditions 
without  phosphorus ;  that  is,  with  lime,  nitrogen,  and  potassium 
(7)  the  yields  in  pounds  per  acre  were  1,760  and  2,080  without  and 
with  bacteria,  respectively,  and  these  yields  were  increased  to  2,560 
and  3,520,  respectively,  by  the  addition  of  phosphorus  (9).  The 
inoculated  pot  receiving-  lime  and  potassium  (5)  yielded  at  the  rate 
of  1,120  pounds  per  acre,  but,  where  phosphorus  was  added  to  this 
combination  (8),  the  yield  became  2,720  pounds. 

EFFECT  OF  POTASSIUM. 

Applications  of  the  element  potassium  produced  a  slight  in- 
crease in  yield  when  added  after  sufficient  nitrogen  was  provided, 
(3,  7),  but  the  increase  becomes  more  marked  when  the  potassium 
is  added  after  both  nitrogen  and  phosphorus  have  been  supplied. 
For  example,  with  both  lime  and  phosphorus  added,  and  nitrogen 
accumulated  by  the  alfalfa  bacteria,  the  yield  was  1,600  pounds 
without  potasssium  (4)  and  2,720  pounds  with  potassium  (8);  and, 
when  an  innoculated  pot  was  also  given  an  application  of  nitrogen 
(6),  it  yielded  at  the  rate  of  3,040  pounds  without  potassium  and 
3,520  pounds  with  potassium. 

THE  RELATIVE  EFFECT  OF  NITROGEN,  PHOSPHORUS,  AND 
POTASSIUM. 

The  relative  value  of  nitrogen,  phosphorus,  and  potassium  for 
the  growth  of  alfalfa  may  best  be  determined  by  the  maximum 
yields  produced  when  each  of  the  elements  in  turn  was  not  sup- 
plied. 

Thus,  the  maximum  yield  per  acre  with  no  addition  of  nitro- 
gen (either  direct  or  by  means  of  bacteria)  was  320  pounds. 

The  maximum  yield  without  addition  of  phosphorus  was  2,080 
pounds  (7). 

The  maximum  yield  without  addition  of  potassium  was  3,040 
pounds  (6). 

The  maximum  yield  without  the  addition  of  lime  was  3,200 
pounds  (10). 

The  maximum  yield  with  all  of  these  supplied  was  3,520 
pounds  (9). 

In  other  words,  the  losses  resulting  from  a  failure  to  add  to 
•ihe  soil  these  different  elements  of  fertility  would  be  as  follows  : 


1902.]  ALFALFA  ON  ILLINOIS  SOIL.  323 

"With  nitrogen  not  applied  the  maximum  loss  is  3,200. 

With  phosphorus  not  applied  the  maximum  loss  is  1,440. 

With  potassium  not  applied  the  maximum  loss  is  480. 

These  figures  fairly  represent  the  relative  values  of  additions 
of  nitrogen,  phosphorus,  and  potassium  (each  after  the  other  ele- 
ments have  been  supplied)  to  the  soil  which  was  used  in  these  pots. 
For  field  conditions  the  figures  for  nitrogen  and  phosphorus  are 
probably  nearly  correct,  relatively,  but  the  figure  for  potassium  is 
probably  too  high  because  of  the  fact  that  the  subsoil  is  richer  in 
potassium  than  is  the  surface  soil,  and  under  field  conditions  the 
alfalfa  roots  would  have  access  to  the  potassium  in  the  subsoil.  As 
the  subsoil  usually  contains  somewhat  less  phosphorus  and  very 
much  less  nitrogen,  than  the  surface  soil,  the  field  conditions  would 
be  but  little  better  than  the  pots  for  furnishing  those  two  elements. 
It  should  be  remembered  that  no  conclusions  can  be  drawn  as  to 
the  relative  value  of  applying  lime  to  the  soil  used  because  of  the 
fact  that  the  water  used  in  all  of  the  pots  contained  a  trace  of 
lime. 

There  is  evidence  that  both  phosphorus  and  potassium  have  an 
indirect  value  aside  from  their  direct  value  as  plant  food  for  the  al- 
falfa. This  is  the  value  of  these  elements  to  the  bacteria.  Bacte- 
ria themselves  are  living  plants,  and  while  they  are  microscopic  in 
size  they  are  almost  infinite  in  number,  and  their  multiplication 
and  development  are  largely  dependent  upon  the  supply  of  availa- 
ble mineral  elements  of  plant  food.  It  will  be  observed  that  a  yield 
of  2,080  pounds  per  acre  (7)  was  secured  without  the  addition  of 
phosphorus.  The  yield  became  3,520  pounds  when  phosphorus  was 
applied  (9).  This  increase  of  1,440  pounds  per  acre  may  be  due  in 
part  to  the  direct  value  of  the  phosphorus  to  the  alfalfa  and  in  part 
to  its  value  in  promoting  the  development  of  the  bacteria  and  thus 
increasing  the  supply  of  nitrogen  which  the  bacteria  secure  from 
the  air  and  furnish  to  the  growing  alfalfa.  Again,  the  addition  of 
phosphorus  to  the  combination,  lime,  potassium,  bacteria,  increased 
the  yield  from  1,120  (5)  to  2,720  (8),  an  increase  of  .1,600  pounds 
per  acre.  The  fact  that  the  soil  itself  contained  sufficient  phospho- 
rus to  produce  a  yield  of  2,080  pounds  (7)  tends  to  prove  that  the 
first  960  pounds  of  this  1,600  pounds  increase  was  due  to  the  in- 
creased development  of  the  bacteria  resulting  from  the  additional 
supply  of  available  phosphorus  ;  the  remainder  of  the  increase,  640 
pounds,  is  probably  due  to  both  the  direct  and  the  indirect  value  of 
the  phosphorus. 

Without  addition  of  potassium  the  maximum  yield  was  3,040 
pounds  (6),  consequently  the  increase  in  yield  from  1,600  pounds 


324 


BULLETIN    NO.  76. 


(4)  to  2,720  pounds  (8),  resulting-  from  the  addition  of  potassium 
to  the  combination,  lime,  phosphorus,  bacteria,  was  probably 
largely  due  to  the  increased  development  of  the  bacteria  in  the 
presence  of  a  larger  supply  of  available  potassium. 

The  field  experiments,  which  are  described  further  on,  give 
abundant  evidence  of  the  value  of  applications  of  lime  in  promot- 
ing- the  development  of  the  alfalfa  bacteria. 

It  seems  probable  that,  after  an  alfalfa  field  has  been  inocu- 
lated for  two  or  three  years  and  the  soil  has  become  thoroughly  in- 
fected with  the  bacteria,  it  will  not  be  so  necessary  to  add  liberal 
supplies  of  the  mineral  elements  of  plant  food  as  it  is  during  the 
early  stages  of  inoculation  when  there  are  comparatively  few  bac- 
teria in  the  soil  and  their  multiplication  is  so  important.  There 
are  some  results  from  the  pot  cultures  and  also  from  the  field  ex- 
periments which  indicate  that  as  the  inoculation  becomes  more 
thoroug-h,  less  benefit  is  derived  from  applications  of  the  mineral 
elements. 

The  photographic  reproduction  of  the  six  pots  receiving  no 
artificial  fertilizer,  three  of  which  were  inoculated  and  three  unin- 
oculated,  as  they  appeared  on  May  11,  less  than  three  weeks  after 
cutting  off  the  crops  discussed  above,  may  be  of  additional  interest. 

Cutting-s  made  from  these  six  pots  on  May  21,  just  four  weeks 
after  the  previous  cutting's,  gave  the  results  shown  in  Table  4. 

TABLE  4.    ALFALFA  POT  CULTURES  ;  CUT  MAY  21,  1902.    WEIGHTS  IN  GRAMS 
PER  POT  AND  POUNDS  PER  ACRE. 


Serial  No. 

Pot 

No. 

Treatment  applied 

Green  alfalfa 
(gms.  per  pot) 

Air-dry  hay 

(gms.  per  pot) 

Air-dry  hay 
(  Ib.  per  acre  ) 

I 

I 

ii 

II 

12 
12 

25 
37 

35 
47 

36 
48 

0:   

7 
42 

8 
33 

6 
33 

i 

12 

2 

8 

2 
IO 

160 
1920 

320 
1280 

320 
1600 

0:  Bacteria  

0:    

0:  Bacteria 
0:    

0:  Bacteria 

It  will  be  observed  that  the  highest  yield  of  the  three  uninocu- 
lated  pots  was  320  pounds  per  acre,  while  the  average  yield  of  the 
three  inoculated  pots  was  1,600  pounds, — five  times  as  great. 
These  results  only  serve  to  confirm  those  secured  from  the  preced- 
ing crops,  and  to  show  the  value  of  the  inoculation  in  a  most  conclu- 
sive manner. 


1 902.  ] 


ALFALFA  ON  ILLINOIS  SOIL. 


M 

M 

P 

a 

D 
U 

H 
O 

PH 


326  BULLETIN    NO.    76.  [Jllfy* 

When  we  remember  that  the  twenty-four  pots  used  in  this  series- 
of  experiments  were  all  filled  with  the  same  kind  of  well  mixed  soil, 
and  that  this  soil  is  fairly  representative  of  thousands  of  square  miles- 
of  Central  Illinois  land,  that  both  series,  of  twelve  pots  each,  were 
kept  on  the  same  table  in  the  greenhouse,  watered  at  the  same  times 
with  exactly  the  same  kind  of  water,  and  in  every  way  treated  ex- 
actly alike,  except  that  one  series  was  inoculated  with  alfalfa  bac- 
teria while  the  other  series  was  not  inoculated,  then  these  most 
positive  and  conclusive  results,  as  shown  by  the  records  of  the  ex- 
periment, including1  the  color  of  the  foliage,  the  height  of  the 
growing-  plants,  the  photographic  reproductions,  and  the  absolute 
yields  per  pot  and  rate  of  yield  per  acre,  seem  truly  remarkable  and 
appear  to  be  of  tremendous  importance  in  solving-  the  question, 
Why  is  alfalfa  so  commonly  an  unsuccessful  crop  on  Illinois  soils? 

FIELD  EXPERIMENTS  WITH  ALFALFA. 

An  acre  of  ordinary  slightly  rolling  black  prairie  land  was 
seeded  with  alfalfa  in  June,  1901.  The  soil  was  considerably  better 
than  ordinary  cultivated  soil  (such  as  was  used  in  the  pot  culture 
experiments).  Previous  to  1895,  it  had  been  in  pasture  for  at  least 
eighteen  years,  and  since  1897  it  had  been  in  meadow  ;  thus,  only- 
three  grain  crops  (corn  in  1895,  1896,  and  1897)  were  grown  on 
this  soil  during  the  past  twenty-five  years.  The  field  which  was 
8  rods  wide  east  and  west,  and  20  rods  long  north  and  south,  ex- 
clusive of  some  border  and  division  strips,  was  divided  into  two 
parts  by  a  line  running  north  and  south,  and  into  five  parts  by- 
lines running  east  and  west.  The  west  part  of  the  acre  was  inoc- 
ulated with  soil  taken  from  an  old  alfalfa  field  in  Kansas.  The 
five  divisions  from  north  to  south  were  fertilized  as  follows  : 

Plot  No.  1— Check  (nothing  applied). 

Plot  No.  2  —Lime. 

Plot  No.  3 — Lime  and  phosphorus. 

Plot  No.  4 — Lime  and  potassium. 

Plot  No.  5 — Lime,  phosphorus,  and  potassium. 

The  west  part  of  each  of  these  plots  was  inoculated  ;  the  east 
part  was  not  inoculated.  The  arrangement  of  the  plots  can  be 
plainly  seen  from  the  following  diagram. 


IQ02.] 


ALFALFA  ON  ILLINOIS  SOIL. 


327 


2. 


4- 


The  rates  applied  per  acre  were: 
320  pounds  of  air-slacked  lime,  320 
pounds  of  bone  meal  (containing 
30  per  cent,  phosphoric  oxid),  and 
160  pounds  of  potassium  sulfate. 

The  infected  alfalfa  soil  was 
applied  at  different  rates  of  seed- 
ing- on  narrow  strips  running 
north  and  south  on  the  west  part 
of  the  field,  the  lightest  applica- 
tion, 320  pounds,  being  on  the 
west  side,  and,  on  successive  strips 
eastward,  the  rates  of  application 
were  640,  960,  1,280,  1,600,  and 
1,920  pounds,  respectively.  Each 
of  these  strips  was  about  one-half 
rod  wide  with  a  very  narrow  un- 
inoculated  division  strip  (about 
two  feet)  between  them.  A  bor- 
der strip  about  four  feet  wide  on 
the  extreme  west  side  was  not  in- 
oculated. A  good  stand  of  young- 
plants  was  secured,  but  a  very 
heavy  rain  storm,  which  occurred 
on  July  2,  washed  the  soil  some- 
what, and,  as  the  west  side  of  the 
field  was  somewhat  higher  than 
the  east  side,  it  was  feared  that  the 
bacteria  might  be  carried  over 

the  east  plots  and  thus  inoculate  the  whole  field  to  some  extent, 
which  afterward  proved  to  be  the  case,  particularly  along  the  east 
side  where  the  water  stood  for  a  short  time.  The  southeast  quarter 
of  the  field  was  the  lowest  part,  and,  although  it  was  tile  drained, 
the  water  stood  on  it  long  enough  to  kill  most  of  the  alfalfa  plants. 
Because  of  these  occurrences,  the  results  of  the  experiment  are  prob- 
ably not  so  marked  as  they  would  otherwise  have  been. 

During  the  summer  of  1901,  the  alfalfa  was  clipped  three 
times,  the  clippings  being  left  lying  on  the  field.  During  midsum- 
mer, the  weeds  seemed  to  grow  faster  than  the  alfalfa,  but  with 
each  clipping  the  alfalfa  improved,  and  in  the  fall  the  stand  was 
good  where  it  had  not  been  injured  by  the  water  standing  on  it. 

No  marked  differences  were  noted  among  the  different  plots, 
excepting  that  the  alfalfa  made  a  much  more  vigorous  growth 


No  Fertilizer 
Bacteria 

No  Fertilizer 

Lime 
Bacteria 

Lime 

Lime 
Phosphorus 
Bacteria 

Lime 
Phosphorus 

Lime 
Potassium 
Bacteria 

Lime 
Potassium 

Lime 
Phosphorus 
Potassium 
Bacteria 

Lime 
Phosphorus 
Potassium 

PLAN  OF  PLOT  EXPERIMENTS 
WITH  ALFALFA. 


328  BULLETIN  NO.  76. 

wherever  phosphorus  had  been  applied,  the  line  being-  very  notice- 
able where  the  application  of  phosphorus  began. 

In  the  fall  tubercles  were  found  in  abundance  upon  the  plants 
growing-  in  the  strips  of  land  where  the  heaviest  applications  of  in- 
fected soil  were  made,  but  none  were  found  on  plants  in  the  unin- 
oculated  soil. 

In  the  spring1  of  1902  the  alfalfa  began  to  grow  vigorously  and 
was  entirely  free  from  weeds,  but  within  a  short  time  some  very 
marked  differences  appeared  among  the  different  plots.  The  effect 
of  the  inoculation  became  very  apparent,  all  of  the  inoculated  soil 
producing  a  much  more  vigorous  growth  than  occurred  on  uninoc- 
ulated  soil,  and  the  more  vigorous  growth  was  accompanied  by  a 
dark  green  healthy  looking  color  in  the  growing  alfalfa,  while  the 
plants  on  uninoculated  soil  took  on  a  pale  green  color  indicative  of 
an  insufficient  supply  of  nitrogen.  This  difference  in  growth  and 
color  between  inoculated  and  uninoculated  plants  was  very  marked 
even  where  no  fertilizer  was  applied,  but  it  was  more  marked  where 
lime  was  applied  and  still  more  marked  where  both  lime  and  phos- 
phorus were  applied.  These  differences  are  apparent  in  the  photo- 
graphic reproductions  although  the  photographs  do  not  fully  bring 
out  the  striking  differences  which  existed  in  the  field  and  which 
were  observed  by  several  hundred  farmers  from  different  sections 
of  Illinois  who  visited  the  University  about  the  time  these  photo- 
graphs were  taken. 

Plate  4  shows  on  the  left  uninoculated  and  unfertilized  soil, 
on  the  right  inoculated  and  unfertilized  soil.  The  difference  in 
growth  is  measured  by  the  stakes  and  the  difference  between  two 
shades  of  the  same  color  is  shown  remarkably  well  for  a  photo- 
graphic reproduction.  The  north  line  of  plot  No.  2,  to  which  an 
application  of  320  pounds  per  acre  of  air-slacked  lime  had  been 
made,  coincides  with  the  top  of  the  right  hand  label  and  the  effect 
of  the  lime  upon  the  growth  and  color  of  the  alfalfa  is  very  appar- 
ent. Undoubtedly  the  beneficial  effect  of  the  lime  is  indirect,  the 
development  and  activities  of  the  bacteria  being  promoted  by  the 
presence  of  a  base  and  the  neutralizing  of  the  soil  acids.  The 
effect  of  lime  upon  the  uninoculated  soil  on  the  left  is  very  slight, 
and  even  this  slight  effect  is  produced  in  narrow  crooked  strips 
running  to  the  eastward,  which  were  evidently  little  water  courses 
during  the  storm  above  referred  to,  and  which  became  more  or  less 
infected  with  alfalfa  bacteria.  The  still  lower  ground  along  the 
east  side  of  the  field  was  found  to  be  thoroughly  infected  and  the 
alfalfa  there  grew  as  vigorously  as  on  the  west  side  of  the  field 
where  the  application  of  infected  soil  was  made.  A  close  inspec- 


1902.] 


ALFALFA  ON  ILLINOIS  SOIL. 


329 


c 
u 

TJ 

2  1 

-^  o 

y  O 

H  <U 

<     — 


H  tW 

j  "B, 

P  a 

cj  re 

O  D 

^  S 


33° 


BULLETIN  NO.  76. 


[July, 


IQ02.] 


ALFALFA  ON  ILLINOIS  SOIL. 


331 


O 
Cfl 


O    O 

H  a 

U   PH 


332  BULLETIN  NO.  76.  {July, 

tion  of  the  right  hand  side  of  the  field  will  discover  light-colored 
narrow  strips  running-  north  and  south.  These  are  the  uninocu- 
lated  two-foot  strips  between  the  different  rates  of  application  of 
alfalfa  soil  already  explained. 

Plate  5  shows  very  imperfectly  the  effect  of  the  inoculation  on 
the  limed  soil.  These  label  stakes  are  tivo  feet1  high  and  serve  as 
a  measure  of  the  height  of  the  alfalfa.  The  difference  in  thickness  of 
stand  can  be  seen  but  the  difference  in  color  between  the  inoculated 
and  uninoculated  alfalfa  is  not  brought  out  in  the  photograph. 

Plate  6  shows  the  effect  of  inoculating1  soil  to  which  both  lime 
and  phosphorus  had  been  applied,  the  inoculated  soil  producing-  a 
markedly  increased  growth  of  alfalfa  over  the  uninoculated  soil. 
To  the  southwest  may  be  seen  the  patch  of  ground  where  the  alfalfa 
was  destroyed  by  water,  on  account  of  which  no  results  were  se- 
cured from  plots  4  and  5. 

By  comparison  of  Plates  4,  5,  and  6,  it  will  be  seen  that  both 
lime  and  lime  with  phosphorus  are  applied  to  the  soil  under  field 
conditions  with  marked  advantage  to  the  alfalfa  provided  with 
bacteria.  It  is  true  that  the  applications  of  lime  and  of  lime  with 
phosphorus  to  the  uninoculated  soil  produced  increased  growth  of 
alfalfa,  but,  as  already  explained,  this  occurred  principally  on  nar- 
row crooked  strips  or  upon  the  lower  ground  which  had  become  in- 
oculated. Abundance  of  tubercles  are  found  on  the  roots  of  the 
dark  green  plants  growing  in  those  places,  while  the  pale  green 
plants  as  a  rule  have  no  tubercles,  although  the  entire  field  is  fast 
becoming  inoculated,  the  bacteria  evidently  being  scattered  over 
the  field  by  wind  and  water  and  no  doubt  by  the  hay  rake  and  other 
implements  also. 

Because  of  this  cross  inoculation  no  truthful  results  as  to  yield 
could  be  secured  by  harvesting  the  entire  plots,  but  fairly  reliable 
results  were  obtained  by  harvesting  small  plots,  although  in  every 
case  the  yield  from  the  uninoculated  plot  is  undoubtedly  too  high 
owing  to  the  cross  inoculation. 

Table  5  gives  the  yield  per  acre  of  air-dry  hay  from  one- 
thousandth  acre  plots,  the  inoculated  plots  being  measured  off  on 
the  strip  where  the  heaviest  application  of  infected  soil  was  made. 

It  will  be  seen  that  the  inoculated  plots  yielded  about  twice  as 
much  hay  as  the  uninoculated  plots. 


I.     The  stakes  shown  in  Plate  4  were  3  feet  high. 


igo2j 


ALFALFA  ON  ILLINOIS  SOIL. 


333 


TABLE  5.    ALFALFA  FIELD  EXPERIMENTS  ;  FIRST  CUTTING  1902,  MAY  28. 
WEIGHT  IN  POUNDS  PER  PLOT  AND  PER  ACRE. 


Plot  No. 

Treatment  applied 

Green    alfalfa 
(Ib.  per  plot) 

Air-dry  hay 
(Ib.  per  plot) 

Air-dry  hay 
(Ib.  per  acre) 

I 

0:  

5K 

i-f56 

I^IT 

I 

2 

0:  Bacteria 
L:  

ii 

6 

*A 

Il7R 

»J*J 

2563 

Id-jg 

2 
T. 

L:  Bacteria 
LP:  

12 

T\i 

*i 

Hr 

•2875 

iQ>8 

3 

LP:  Bacteria 

15 

31 

3625 

Plate  7  is  made  from  a  photograph  of  the  bundles  of  alfalfa 
hay  harvested  from  these  thousandth-acre  plots,  and  well  illustrates 
the  relative  differences  in  the  yield  of  hay  from  the  inoculated  and 
uninoculated  plots  ;  (1)  with  no  fertilizer  applied,  (2)  with  lime 
applied,  (3)  with  lime  and  phosphorus  applied.  For  reasons  al- 
ready explained,  no  trustworthy  yields  could  be  taken  from  plots 
larger  than  one-thousandth  acre  on  uninoculated  soil. 

The  entire  field  of  alfalfa  was  cut  on  June  7,  and  the  exact 
yield  of  air-dry  hay  was  taken  on  six  fortieth-acre  plots,  all  of  which 
had  been  inoculated.  The  first  two  are  duplicate  plots  from  that 
part  of  the  field  which  had  been  inoculated  but  had  received  no 
fertilizer.  The  second  two  are  duplicates  from  the  inoculated  part 
which  had  received  an  application  of  lime.  The  third  two  are 
duplicate  plots  from  the  part  of  the  field  which  had  been  inocu- 
lated and  had  also  received  lime  and  phosphorus.  Table  6  g-ives 
the  yields  per  plot  and  rate  of  yield  per  acre. 

TABLE  6.    ALFALFA  FIELD  EXPERIMENTS  ;  FIRST  CUTTING  1902,  JUNE  7. 
WEIGHT  IN  POUNDS  PER  PLOT  AND  PER  ACRE. 


Plot  No. 

Treatment  applied 

Air-dry  hay 
(  Ib.   per  plot) 

Air-dry  hay 
(Ib.  per   acre) 

i-a 
i-b 

0:  Bacteria 
0:  Bacteria 

57 
57 

2280 
2280 

average  

ey 

2280 

2-a 
2-b 

L:   Bacteria 
L:   Bacteria 

97 
86 

3880 
3440 

average  

Ql/4 

^660 

3-a 

3-b 

LP:  Bacteria 
LP:  Bacteria 

116 

123 

4640 
4800 

average  

118 

4720 

334 


BULLETIN  NO.  76. 


[July, 


s  «j 

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W    tn 


1902.]  ALFALFA  ON  ILLINOIS  SOIL.  335 

It  will  be  observed  that  after  having-  been  inoculated  the  plots 
receiving-  no  fertilizer  yielded  2,280  pounds  of  hay  per  acre,  the 
plots  receiving1  lime  yielded  an  averag-e  of  3,660  pounds,  and  the 
plots  receiving-  both  lime  and  phosphorus  yielded  an  averag-e  of 
4,720  pounds,  the  yield  on  inoculated  soil  having-  been  increased 
more  than  50  per  cent,  by  the  lime  alone,  and  more  than  100  per 
cent,  by  applications  of  both  lime  and  phosphorus.  These  differ- 
ences are  more  marked  than  were  the  yields  from  the  corresponding" 
thousandth-acre  plots,  because  the  smaller  plots  were  harvested 
more  than  a  week  earlier,  and  also  because  of  the  fact  that  the 
thousandth-acre  plots  were  measured  off  in  the  strip  which  had 
been  treated  with  alfalfa  soil  at  the  rate  of  nearly  one  ton  per  acre, 
while  the  fortieth-acre  plots  extended  over  the  strips  which  had 
received  lighter  applications  of  the  infected  soil.  The  difference 
between  the  lig-ht  and  heavy  inoculations  was  much  more  marked 
on  the  unfertilized  soil  than  on  the  fertilized  soil.  The  application 
of  lime,  and  more  especially  that  of  both  lime  and  phosphorus, 
seemed  to  so  promote  the  development  of  the  bacteria  that  even  the 
lig-htest  application  (320  pounds  of  infected  soil  per  acre)  was  very 
effective  as  compared  with  no  inoculation. 

Undoubtedly  an  application  of  one  hundred  pounds  per  acre  of 
soil  thoroug-hly  infected  with  alfalfa  bacteria  tog-ether  with  three 
or  four  hundred  pounds  of  lime  would  in  the  course  of  a  year  or 
two  effect  a  very  satisfactory  inoculation  of  ordinary  Illinois  soil, 
and  it  seems  very  evident  that  an  application  of  two  or  three  hun- 
dred pounds  per  acre  of  some  suitable  phosphorus  fertilizer ,  such 
as  steamed  bone  meal,  raw  bone  meal,  rock  phosphate,  or  basic 
phosphate,  in  the  fall,  or  acidulated  bone  meal  or  other  superphos- 
phate, in  the  spring-,  would  be  to  the  advantag-e  of  the  alfalfa  and 
to  the  profit  of  the  grower.  If  alfalfa  hay  is  worth  $8  a  ton1,  then 
according-  to  the  results  given  in  Table  6,  the  application  of  320 
pounds  of  air  slacked  lime,  which  increased  the  yield  of  air-dry  hay 
from  2,280  pounds  to  3,660  pounds  per  acre,  a  net  increase  of  1,380 
pounds,  was  worth  $5.52  to  the  grower  for  its  effect  upon  the  first 
cutting-  of  the  second  year.  Likewise  the  application  of  320  pounds 
of  acidulated  bone  meal  (worth  about  $3.20)  which  produced  an 
additional  net  increase  of  1,060  pounds  of  hay,  was  worth  $4.24  to 
the  grower,  and  the  total  increase  of  2,440  pounds  of  hay  per  acre, 
resulting-  from  the  application  of  both  lime  and  phosphorus,  would 
be  worth  $9.76  per  acre,  for  one  cutting-. 


I.  Alfalfa  hay  is  worth  about  the  same  as  red  clover,  which  varies  from  $6.00 
to  $10.00  or  $i2.co  per  ton  in  this  section  of  the  country. 


336. 


BULLETIN  NO.  j6. 


(July, 


On  July  21  the  second  cutting1  of  1902  was  made  of  alfalfa  from 
the  same  inoculated  plots  referred  to  in  Table  6  ;  that  is,  from  the 
inoculated  pl©ts  which  had  received  (1)  no  fertilizer,  (2)  lime,  and 
(3)  lime  and  phosphorus,  the  yields  being- taken,  as  before,  on  dupli- 
cate fortieth-acre  plots.  The  yields  oO  air-dry  hay  are  given  in 
Table  6  (b). 

TABLE  6  (b).    ALFALFA  FIELD  EXPERIMENTS  ;  SECOND  CUTTING  1902,  JULY  21. 
WEIGHT  IN  POUNDS  PER  PLOT  AND  PER  ACRE. 


Plot    No. 

Treatment  applied. 

Air-dry  hay 
(Ib.   per   plot) 

Air-dry  hay 
(Ib.    per  acre) 

i-a 
i-b 
average  

0; 
0: 

Bacteria 
Bacteria 

75 
78 

3,000 
3,120 

76^ 

3,060 

2-a 
2-b 
average.  .  . 

L: 
L: 

Bacteria 
Bacteria 

104 

IOO 

4,160 
4,000 

1  02 

4,080 

3-a 
3-b 

LP 
LP 

Bacteria 
Bacteria 

134 
130 

5.36o 
5,200 

average. 


132 


5280 


These  results  are  in  accord  with  those  obtained  from  the  first 
cutting-,  on  June  7,  although  the  yields  from  the  second  cutting- 
are  somewhat  larg-er.  It  should  be  stated  that  these  yields  are  on 
the  basis  of  thoroughly  air-dried  hay  (not  merely  field-cured). 
The  duplicate  determinations  agree  well,  and  show  an  average 
yield  of  more  than  1^  tons  per  acre  on  unfertilized  soil,  which  was 
increased  to  two  tons  on  the  limed  soil  and  to  more  than  2%  tons 
on  the  soil  to  which  both  lime  and  phosphorus  had  been  applied. 

After  the  inoculation  with  bacteria,  the  effect  of  the  lime  was 
to  increase  the  yield  by  1,020  pound,  and  a  still  further  increase  of 
1,200  pound  was  produced  by  the  phosphorus.  Applications  of  both 
lime  and  phosphorus  increased  the  yield  over  no  fertilizer  by 
2,220  pounds  per  acre.  The  total  yields  of  the  first  and  second  cut- 
tings added  together  were  5,280  pounds  of  air-dry  hay  from  the 
unfertilized  soil,  7,740  pounds  from  the  limed  soil,  and  exactly  10,- 
000  pounds  (5  tons)  from  the  soil  which  had  received  both  lime  and 
phosphorus. 


1Q02.]  ALFALFA  ON  ILLINOIS  SOIL  337 

THE  FIXATION  OF  ATMOSPHERIC  NITROGEN  BY 

ALFALFA. 

The  investigations  of  Atwater  in  America,  Boussingault  and 
Viile  in  France,  Hellriegel,  Willfarth,  and  Nobbe  in  Germany,. 
Lawes  and  Gilbert  in  England,  et  al.,  have  fully  established  the 
scientific  facts  ;  (1)  that  leguminous  plants,  as  the  clovers,  peas, 
beans,  vetches,  alfalfa,  etc.,  have  the  power  to  gather,  or  accum- 
ulate, free  nitrogen  from  the  atmosphere;  (2)  that  this  fixation  of 
free  nitrogen  is  actually  accomplished  by  microscopic  organisms 
called  bacteria  which  live  in  little  nodules,  or  tubercles,  upon  the 
roots  of  the  legumes  ;  and  (3)  that,  for  different  species  of  legu- 
minous plants,  there  are  also  different  species  of  "  nitrogen  gath- 
ering" bacteria.  Many  investigations  have  also  been  conducted  to 
determine  the  amounts  of  nitrogen  which  can  be  fixed  by  different 
leguminous  plants,  but  these  experiments  have  actually  been  car- 
ried on  in  pure  sand  cultures  under  conditions  which  necessitate 
that  all  nitrogen  which  the  legume  secures  must  be  obtained  from 
the  air. 

There  is  abundance  of  evidence  that  leguminous  plants  secure 
some  nitrogen  from  the  air  when  grown  in  ordinary  soil,  if  they  are 
provided  with  the  bacteria.  Indeed,  the  presence  of  the  tubercles 
upon  the  roots  is  one  of  the  evidences  that  free  nitrogen  is  being 
fixed,  and  another  evidence  of  that  fact  is  found  in  the  beneficial 
effects  of  clover  and  other  legumes  in  crop  rotations.  It  is  a  sim- 
ple matter  to  determine  how  much  nitrogen  is  contained  in  a  ton 
of  clover  ;  but,  after  the  amount  is  determined,  it  still  remains  a 
question  as  to  how  much  of  the  nitrogen  was  taken  directly  from 
the  soil  and  how  much  was  secured  from  the  air,  and  a  question 
very  frequently  asked  is,  How  much  of  their  nitrogen  do  legumi- 
nous crops  obtain  from  the  air  and  how  much  do  they  actually  take 
from  the  soil? 

The  pot  culture  and  field  experiments  described  in  the  preced- 
ing pages  were  conducted  on  ordinary  soil  and  in  such  a  manner 
that  it  can  be  determined  with  a  high  degree  of  accuracy  how  much 
nitrogen  was  secured  from  the  air  by  the  alfalfa.  This  is  due  to 
the  fact  that,  in  all  cases,  alfalfa  was  grown  not  only^with  bacteria 
present  but  also  in  exactly  similar  duplicate  pots  or  plots  with  bac- 
teria absent,  and  the  difference  between  the  amounts  of  nitrogen 
contained  in  the  crop  from  the  inoculated  soil,  on  the  one  hand,  and 
in  the  crop  from  the  uninoculated  soil,  on  the  other  hand,  repre- 
sents the  amount  of  nitrogen  which  was  secured  from  the  atmos- 
phere by  the  bacteria.  In  no  case  will  this  amount  be  larger  than 
the  actual  truth  ;  but,  if  the  soil  which  was  not  intentionally  inoc- 


338 


BULLETIN  NO.  76. 


te, 


\ 


PLATE  8.  ALFALFA  PLANTS,  SHOWING  AN  UNINOCULATED  PLANT  ON  THE  LEFT  AND 
AN  INOCULATED  PLANT,  WITH  ROOT  TUBERCLES  AND  INCREASED  GROWTH, 
ON  THE  RIGHT. 


1902.] 


ALFALFA  ON  ILLINOIS  SOIL. 


339 


ulated  was  nevertheless  to  some  extent  infected  with  alfalfa  bacte- 
ria by  cross  inoculation,  then  the  amount  of  nitrogen  actually  se- 
cured from  the  air  would  be  even  larger  than  represented  by  these 
determinations.  Plate  8  shows  an  uninoculated  alfalfa  plant  on 
the  left  and  on  the  right  an  inoculated  plant  with  clusters  of  tu- 
bercles in  which  the  bacteria  live,  upon  its  roots,  and  its  increased 
growth  illustrates,  in  no  exaggerated  manner,  the  effect  of  inoc- 
ulation on  individual  plants. 

FIXATION  OF  NITHOGEN  BY  POT  CULTURES. 
Table  7  gives  in  pounds  per  acre  the  amounts  of  dry  matter 
and  of  nitrogen  in  t  he  crops  cut  from  the  pot  cultures  on  April  23, 
1902  ;  also  the  pe  rcentage  of  nitrogen  in  the  dry  matter  and  the 

TABLE  7-    FIXATION  OF  NITROGEN  BY  ALFALFA  IN  POT  CULTURES  :  CROPS  CUT 

APRIL  23,  1902. 


Serial 
No. 

Pot 

No. 

Treatment  applied 

Dry  matter 
in  crop 
(Ib.  per  acre) 

Nitrogen 
in 
dry  matter 
(percent) 

Nitrogen 
in  crop 
(Ib.  per  acre) 

Nitrogen 
fixed 
by  bacteria 
(Ib.  per  acre) 

I 

2C 

0:    7  

280 

2.61 

7.^1 

i 

2 

37 
?6 

0:  Bacteria 
L:  

1300 

280 

4.09 
^.47 

53-17 

O   72 

45-86 

2 
1 

38 

27 

L:  Bacteria 
LN:   

IOIO 

1280 

4.24 
4  48 

42.82 

C7     OT 

33-10 

3 

A 

39 
38 

LN:  Bacteria 
LP:  

1450 
140 

4.48 
2   78 

64.96 
-1  80 

7-65 

4 

E 

40 

29 

LP:  Bacteria 
LK:  

1440 
140 

4.08 
-j    Cn 

58.76 

c  en 

54.87 

5 
6 

41 
^O 

LK:  Bacteria 
LNP:  

IOIO 
2280 

4.20 
A     t-l 

42.42 

TOT    m 

37-39 

6 

7 

42 
31 

LNP:  Bacteria 
LNK:  

2780 

1^70 

4OJ 
4.O6 

A     7O 

112.87 

70    7n 

9-32 

7 
8 

43 
32 

LNK:  Bacteria 
LPK:  

1890 

140 

4.38 
1     1C 

82.78 

A     AT 

8.99 

3 

Q 

44 
^^ 

LPK:  Bacteria 
LNPK:  

2480 

2^00 

3-82 
4   OQ 

94-74 

CiA    O7 

90.33 

9 
10 

45 

T.A 

LNPK:  Bacteria 
NPK:  

3230 

2^70 

4.0O 
4    14 

I29.2O 
98    12 

25-13 

10 

II 

£ 

46 

35 

NPK:  Bacteria 
0:    

2940 
280 

4.36 
2.6^ 

I28.I8 

7   ^6 

30.06 

11 

12 

47 
36 

0:  Bacteria 
0:    

730 
280 

4-34 

2   64 

31.68 
7   -JQ 

24.32 

12 

48 

0:    Bacteria 

IO2O 

4.l8 

42.65 

35.26 

340.  BULLETIN  NO.  76. 

amounts  of  nitrog-en  per  acre  obtained  from  the  atmosphere  by  the 
alfalfa  bacteria  in  the  inoculated  pots. 

Where  neither  nitrog-en  nor  bacteria  wore  added  to  the  soil,  all 
of  the  nitrogen  removed  in  the  crops1  must  have  been  derived  from 
the  original  soil.  In  the  three  series  of  pots  receiving  no  fer- 
tilizers (1,  11,  and  12)  the  crops  from  the  uninoculated  pots  con- 
tained 7.31,  7.36,  and  7.39  pounds  of  nitrogen  per  acre,  respective- 
ly, while  53.17,  31.68,  and  42.65  pounds  of  nitrogen  in  the  crop  are 
the  respective  rates  per  acre  of  the  corresponding  inoculated  pots. 
The  average  of  these  is  42.50  pounds  for  the  three  inoculated  pots 
and  7.35  pounds  for  the  three  uninoculated  pots,  making-  an  aver- 
age difference  of  35. 15  pounds  in  favor  of  inoculation.  In  other 
words,  as  an  average  of  three  separate  determinations,  with  no  ap- 
plication of  plant  food,  the  bacteria  "  g-athered''  and  "  fixed  "  and 
furnished  to  the  growing  alfalfa  more  than  35  pounds  of  nitrogen 
per  acre.  At  the  present  average  price  for  nitrog-en  in  commercial 
fertilizers  (15  cents  a  pound)  these  35  pounds  of  nitrogen  are  worth 
#5.25. 

The  addition  of  potassium  without  phosphorus  (5)  gave  no  in- 
crease in  the  amount  of  nitrogen  fixed.  With  phosphorus  added  to 
the  soil,  the  nitrog-en  in  the  crop  was  increased  by  the  presence  of 
the  bacteria  from  3.89  pounds  to  58.76  pounds  per  acre,  54.87 
pounds  of  nitrogen  per  acre  having-  been  fixed  by  the  bacteria. 

Under  the  most  favorable  conditions,  when  both  phosphorus 
and  potassium  were  applied  (8),  still  more  marked  results  were  ob- 
tained, the  nitrog-en  in  the  crop  having-  been  increased  from  4.41 
to  94.74  pounds  per  acre  by  the  bacteria  ;  that  is,  the  bacteria 
gathered  nitrogen  from  the  air  at  the  rate  of  more  than  90  pounds 
per  acre,  which  was  utilized  by  the  growing  alfalfa.  At  market 
prices,  the  nitrogen  gathered  is  worth  $13.50  per  acre. 

It  is  of  interest  to  observe  that  even  in  the  pots  to  which  ap- 
plications of  nitrogen  had  been  made  (3,  6,  7,  9,  10)  some  nitrogen 
was  fixed  when  the  soil  was  inoculated,  ranging  from  7.65  pounds 
per  acre  (3),  with  no  addition  of  phosphorous  or  potassium,  to 
25.13  and  30.06  (9  and  10)  pounds  per  acre  under  the  most  favora- 
ble conditions,  with  applications  of  all  mineral  elements. 

i.  The  amounts  of  nitrogen  given  may  possibly  be  too  high  for  some  of  the 
uninoculated  pots,  because  of  some  cross  inoculation.  The  inoculated  and  unin- 
oculated series  of  pots  stood  side  by  side  on  the  same  table,  and  either  spattering 
of  water  or  more  likely  the  carrying  of  infected  soil  by  ants  (which  were  frequently 
found  in  the  pots)  or  other  insects,  finally  trtnsferred  some  bacteria  to  the  unin- 
oculated series,  which  fact  became  evident,  later  in  the  season  of  1902,  by  the 
development  of  tubercles,  and  the  markedly  increased  growth  of  an  occasional 
plant  in  the  uninoculated  pots. 


1902.] 


ALFALFA  ON  ILLINOIS  SOIL. 


341 


Usually  small  immature  plants  contain  much  higher  percent- 
ages of  nitrogen  than  do  more  fully  developed  plants,  but  it  will  be 
seen  from  Table  7  that,  without  exception,  the  heavy  crops  of 
alfalfa  contained  much  higher  percentages  of  nitrogen  than  the 
lighter  crops.  Triplicate  determinations  of  nitrogen  in  the  crops 
from  unfertilized  pots  (1,  11  and  12)  showed  2.61,  2.63  and  2.64  per 
cent,  of  nitrogen  in  the  dry  matter  from  uninoculated  pots  yielding 
only  280  pounds  of  dry  matter  per  acre,  and  4.09,  4.34  and  4.18  per 
cent,  of  nitrogen  in  the  dry  matter  from  the  inoculated  pots  with 
an  average  yield  of  more  than  1,000  pounds  per  acre.  A  similar 
effect  was  produced  in  all  cases,  whether  nitrogen  was  added  as  a 
a  nitrogenous  fertilizer  or  gathered  by  the  bacteria, — all  of  which 
tends  to  prove  that,  with  insufficient  nitrogen,  the  plants  make  as 
much  growth  as  possible  until  the  fixation  of  carbon  is  practically 
stopped  by  the  lack  of  nitrogen,  as  indicated  by  the  pale  yellowish 
green  color  of  the  folliage. 

Table  8  shows  the  data  relating  to  the  fixation  of  nitrogen  from 
the  next  cutting  (May  21)  of  the  six  unfertilized  pots  (1,  11,  12), 
three  of  which  were  inoculated. 


TABLE  8.    FIXATION  OF  NITROGEN  BY  ALFALFA  IN  POT  CULTURES  ; 

CUT  MAY  21,  1902. 


CROPS 


Serial 
No. 

Pot 
No. 

Treatment  applied 

Dry  matter 
in  crop 
(Ib.  per  acre) 

Nitrogen 
in 
dry  matter 
(percent) 

Nitrogen 
in  crop 
(Ib.  per  acre) 

Nitrogen 
fixed 
by  bacteria 
(Ib.  per  acre) 

i 

2"5 

0:  

140 

2.60 

3-77 

I 
ii 

37 
« 

0:  Bacteria 
0:  

1720 
280 

3-52 
2.47 

60.60 
6.oi 

56.83 

ii 

12 

47 
36 

0:  Bacteria 
0:  

1170 

280 

3.69 
2.61 

43.18 
7.31 

36.27 

12 

48 

0:  Bacteria 

1460 

3.66 

53.48 

46.17 

These  results  only  confirm  those  of  the  previous  cutting  and 
show  that  on  ordinary  unfertilized  Illinois  soil  the  alfalfa  bacteria 
were  capable  of  fixing  46.42  pounds  of  nitrogen  per  acre,  as  the 
average  of  the  three  separate  determinations. 

The  average  percentage  of  nitrogen  in  the  dry  matter  of  the 
crops  from  the  three  uninoculated  pots  was  2.59,  while  3.62  is  the 
average  percentage  from  the  three  inoculated  pots. 


342  BULLETIN  NO.   76.  \_July,. 

FIXATION  OF  NITROGEN  IN  FIELD  EXPERIMENTS. 

Table  9  gives  the  same  data  for  the  field  experiments  as  are 
given  in  Tables  7  and  8  for  the  pot  cultures.  These  determinations 
were  made  on  the  crops  cut  from  the  exact  thousandth-acre  plots 
on  May  28,  1902. 

TABLE  9.    FIXATION  OF  NITROGEN  BY  ALFALFA  IN  FIELD  EXPERIMENTS  ; 
CROPS  CUT  MAY  28,  1902, 


Plot  No. 

Treatment  applied 

Dry  matter 
in  crop 
(Ib.  per  acre) 

Nitrogen  in 
dry   matter 
(percent) 

Nitrogen 
in  crop 
(Ib.  per  acre) 

Nitrogen 
fixed 
by  bacteria 
(Ib.  per  acre> 

i 

0:  

1180 

i  8; 

21    8l 

i 

2 

0:  Bacteria 
L:  

2300 

I^OO 

2.70 

2.  02 

62.04 
26  20 

40.23 

2 

3 

L:  Bacteria 
LP:    

2570 
1740 

2.6S 
2.O^ 

68.02 
ic  .40 

41.82 

3 

LP:   Bacteria 

3290 

.  2.71 

89.05 

53.65 

These  results  secured  under  field  conditions  on  good  black 
prairie  soil  are  in  perfect  agreement  with  the  results  from  the  pot 
culture  experiments,  the  amount  of  atmospheric  nitrogen  fixed  by 
the  alfalfa  bacteria  being-  40.23  pounds  per  acre  on  the  unfertilized 
plot,  41.82  pounds  on  the  limed  plot,  and  53.65  pounds  per  acre  on 
the  plot  receiving-  both  lime  and  phosphorus.  Almost  two-thirds 
of  the  total  nitrog-en  contained  in  the  crop  from  the  inoculated  un- 
fertilized plot  (1)  was  secured  from  the  atmosphere  by  the  alfalfa 
bacteria.  It  should  be  borne  in  mind  that  nitrogen  is  required  for 
root  growth  as  well  as  for  growth  above  ground  and  also  that  these 
amounts  were  obtained  from  a  single  crop  of  alfalfa,  and  that  two 
or  three  more  crops  will  be  cut  during  the  season.  From  the  data 
already  given,  it  will  be  seen  that  on  the  unfertilized  soil  four  such 
crops  as  that  cut  on  May  28  from  the  inoculated  plot  would  mean 
at  least  160  pounds  of  atmospheric  nitrogen  fixed  by  an  acre  of  al- 
falfa during  a  single  year,  and  this  would  require  a  total  yield  of 
only  about  five  tons  of  alfalfa  hay  for  the  season,  which  is  by  no 
means  a  maximum  yield  for  alfalfa  on  Illinois  soil  under  the  most 
favorable  conditions,  as  will  be  shown  in  the  following  pages. 

The  percentage  of  nitrogen  is  much  higher  in  the  crops  from 
the  inoculated  plots,  the  average  being  1.97  per  cent,  in  the  dry 
matter  for  the  uninoculated  plots  and  2.69  for  the  inoculated  plots. 
This  means,  of  course,  that  the  hay  produced  on  the  inoculated 
plots  is  not  only  more  in  quantity,  but  it  is  also  much  better  in 


1902.]  ALFALFA  ON  ILLINOIS  SOIL.  343 

quality,  the  percentage  of  protein  averaging-  only  12.29  in  the  dry 
matter  of  the  uninoculated  crops,  while  16.84  is  the  percentage  for 
the  inoculated  plots. 

THE  PRESENT  STATUS  OF  ALFALFA  IN  ILLINOIS. 

As  stated  in  the  introduction,  "many  different  farmers  have 
tried  to  grow  alfalfa  in  various  sections  of  Illinois,  but  in  most 
cases  it  has  been  pronounced  a  failure."  Nevertheless,  there  are 
some  notable  exceptions  to  this  most  common  experience,  and  it  is 
very  gratifying  and  encouraging  to  be  able  to  state  that  alfalfa  is 
now  growing  with  marked  success  in  a  number  of  places  in  the 
«tate,  and  these  places  are  not  limited  to  Central  Illinois,  but  are 
found  as  far  south  as  Cairo  and  as  far  north  as  the  Wisconsin  line; 
but,  so  far  as  the  writer  has  been  able  to  learn,  by  personal  inves- 
tigations, and  by  examinations  kindly  made  for  me  by  other  per- 
sons, wherever  alfalfa  is  grown  successfully  it  is  either  accompa- 
nied by  the  alfalfa  bacteria  (recognized  by  the  development  of  tu- 
bercles upon  the  alfalfa  roots)  which  are  able  to  supply  the  grow- 
ing plant  with  an  abundance  of  nitrogen  gathered  from  the  air,  or 
it  is  grown  upon  exceedingly  rich  ground  arid  usually  given  large 
yearly  applications  of  barnyard  manure. 

A  field  of  five  acres  of  ordinary  upland  prairie  on  the  farm  of 
Mr.  C.  A.  Haines,  near  Champaign,  Illinois,  was  seeded  to  alfalfa 
in  1899.  The  second  year  fair  crops  of  excellent  hay  were  secured. 
The  third  year  the  crops  were  poor  and  the  plants  looked  yellow 
and  suffering  for  nitrogen.  The  writer  and  about  a  dozen  students 
searched  over  the  field  diligently  at  different  times,  but  were  unable 
to  find  a  single  tubercle  on  the  alfalfa  roots.  A  heavy  dressing  of 
manure  had  been  scattered  over  a  small  part  of  the  field  near  the 
barn  yard  and  on  this  spot  a  most  vigorous  growth  occurred,  but 
no  tubercles  could  be  found  even  on  the  most  vigorous  plants.  In 
June,  1901,  the  Experiment  Station  secured  permission  from  Mr. 
Haines  to  inoculate  a  narrow  strip  across  his  alfalfa  field  with  in- 
fected alfalfa  soil.  Later  in  the  fall  abundance  of  tubercles  ap- 
peared on  the  alfalfa  roots  in  this  strip,  and  in  the  spring  of  1902 
nearly  every  plant  examined  in  this  strip  was  found  to  be  provided 
with  tubercles,  and  occasional  plants  outside  of  the  inoculated  strip 
were  found  with  tubercles  upon  their  roots,  the  bacteria  evidently 
having  been  carried  by  water  or  wind  or  by  the  farm  animals  or  im- 
plements. On  a  part  of  the  field  which  was  so  situated  that  it  could 
not  have  become  infected  by  washings  from  the  inoculated  strip, 
no  tubercles  could  be  found  in  the  early  summer  of  the  present  year. 
Owing  to  the  marked  effect  produced  by  the  manure  in  1901,  Mr. 


344-  BULLETIN  NO.  76.  [July, 

Haines  applied  more  than  20  tons  per  acre  of  barnyard  manure  to 
the  field  (including-  the  inoculated  strip)  during"  the  past  winter. 
Naturally  the  entire  field  is  covered  with  a  rank  growth  at  the 
present  time  and  no  effect  of  the  inoculation  is  observable  ;  indeed, 
before  the  nitrogen  in  the  manure  is  exhausted,  probably  the 
whole  field  will  be  more  or  less  inoculated  and  one  not  acquainted 
with  the  facts  may  be  led  to  suppose  that  manure  has  very  lasting- 
properties  when  applied  to  alfalfa. 

On  the  farm  of  Mr.  W.  R.  Goodwin,  Jr.  (Associate  Editor  of 
the  Breeder's  Gazette),  near  Naperville,  DuPag-e  county,  Illinois, 
on  the  DuPag-e  river,  are  ten  acres  of  alfalfa.  Two  acres  of  this, 
on  the  river  bottom  land,  were  seeded  in  April,  1900  A  g-ood  stand 
resulted  and  a  very  satisfactory  growth  occurred  during1  that  sea- 
son. During-  1901  four  larg-e  crops  of  hay  were  cut  from  this  field, 
a  total  of  21  tons,  by  actual  weight,  of  field  cured  hay  being-  hauled 
off  from  the  two  acres,  making-  a  total  yield  for  the  season  of  10^ 
tons  per  acre  of  excellent  hay. 

In  April,  1901,  Mr.  Goodwin  seeded  four  acres  more  land  ad- 
joining- the  two-acre  field,  and  in  April,  1902,  four  more  acres  were 
seeded,  making-  a  total  of  ten  acres  now  seeded  to  alfalfa.  The 
later  seeding-s  are  upon  somewhat  hig-her  land  than  the  first  field 
seeded. 

Upon  invitation  of  Mr.  Goodwin,  the  writer  examined  this 
alfalfa  field  on  June  9  of  the  present  year. 

More  favorable  conditions  than  this  field  presents  for  the  grow- 
ing- of  alfalfa  are  hard  to  imagine.  The  soil  is  a  rich  deep  loam 
varying  in  color  from  dark  brown  to  black.  It  is  underlaid  with 
limestone,  and  some  limestone  gravel  is  usually  found  near  the 
surface.  Mr.  Goodwin  manures  the  alfalfa  every  year,  and  fur- 
thermore, the  entire  field  is  well  provided  with  alfalfa  bacteria. 
Even  the  young-  plants  only  six  or  seven  weeks  old  had  tubercles  on 
their  roots. 

Plate  9  shows  three  alfalfa  plants  taken  from  Mr,  Goodwin's 
field  on  June  9,  1902.  Oa  the  left  is  a  two  year-old  plant,  in  the 
middle  a  one-year-old  plant,  and  on  the  right  a  young-  plant  six  or 
seven  weeks  old.  Tubercles  were  found  upon  the  roots  of  each  of 
these  plants,  but  most  of  them  were  broken  off  in  removing  the 
dirt  from  the  roots,  although  one  or  more  bunches  of  tubercles  are 
still  showing  upon  the  roots  of  each  plant. 

Several  fields  of  alfalfa  are  growing  near  Cairo,  Pulaski 
county,  Illinois.  They  are  chiefly  on  river  bottom  land  and  are 
making-  very  satisfactory  and  profitable  crops.  A  number  of  these 
fields  were  recently  examined  by  Mr.  W.  O.  Farrin,  a  graduate  stu- 


1902]. 


ALFALFA  ON  ILLINOIS  SOIL. 


345 


PLATE  Q.  "ALFALFA  PLANTS  FROM  FIELD  OF  W.  R.GOODWIN,  JR.,  NEAR  NAPERVILLE. 


346  BULLETIN  NO.  76.  [Julyt 

dent  of  this  College,  and  in  every  case  alfalfa  bacteria  were  found 
to  be  present.  Alfalfa  root  tubercles  have  also  been  found  by  Mr. 
J.  E.  Readhitner,  a  field  assistant  in  the  Illinois  Experiment  Sta- 
tion, in  several  places  in  the  state,  including-  a  field  on  rich  black 
prairie  loam  near  Normal,  and  in  some  other-places  in  Illinois.  Mr. 
D.  S.  Dalbey,  assistant  in  Farm  Crops,  found  tubercles  in  an  al- 
falfa field  belonging-  to  Mr.  Lehman,  near  Sidney. 

The  facts  are  that  the  bacteria  are  certainly  present  in  some 
places  in  the  state  while  in  most  other  places  they  are  certainly 
not  present  in  sufficient  number  to  become  of  appreciable  assist- 
ance to  the  alfalfa  within  three  or  four  years,  and  the  question 
naturally  arises  how  it  happens  that  some  fields  are  already  in- 
fected while  others  are  not.  Of  course,  a  definite  answer  to  thii> 
question  is  not  possible,  neither  is  it  necessary.  We  may  suppose 
that  the  same  bacteria  live  on  some  other  plants  besides  alfalfa  and 
one  of  these  plants  is  native  or  has  been  introduced  in  certain  sec- 
tions. What  seems  more  probable  is  to  suppose  that  a  few  bac- 
teria are  always  carried  with  alfalfa  seed  and  that  if  the  alfalfa 
is  grown  continuously  or  repeatedly  in  any  place  the  soil  will  fi- 
nally become  thoroughly  infected,  and  the  bacteria  will  then  be  car- 
ried by  flood  waters,  dust  storms,  etc.,  over  adjoining-  fields  and 
possibly  for  long-  distances,  especially  along-  river  valleys.  A  sin- 
gle bacterium,  or  possibly  a  hundred,  in  an  acre  of  alfalfa  mig-ht 
not  multiply  and  develop  sufficiently  to  make  their  presence  notice- 
able for  several  years  and  yet  when  we  consider  that  a  single  al- 
falfa plant  under  favorable  conditions  may  have  many  hundred  of 
tubercles  upon  its  roots,  and  that  a  sing-le  tubercle  may  contain  a 
thousand  million  individual  bacteria,  we  realize  the  possible  ra- 
pidity of  their  multiplication ;  and  the  fact  that  a  part  of  Mr. 
Goodwin's  alfalfa  field  was  flooded  by  the  DuPage  river  in  June, 
1902,  is  a  promise  that  any  soils  over  which  those  waters  subse- 
quently flowed  were  thus  inoculated  to  some  extent. 

This  Experiment  Station  seeded  and  inoculated  alfalfa  experi- 
ment fields  in  about  twenty-five  different  places  in  Illinois  the  past 
spring-.  We  have  also  furnished  small  quantities  of  infected  soil 
from  the  University  field  to  farmers  in  different  sections  of  the 
state.  After  the  farmer  has  inoculated  a  few  square  rods  of  his 
alfalfa  field  and  allowed  the  bacteria  to  develop  for  a  year  or  so, 
he  will  then  have  a  sufficient  quantity  of  infected  soil  to  inoculate 
large  areas. 


IQ02.J  ALFALFA  ON  ILLINOIS  SOIL.  347 

DIRECTIONS  FOR  GROWING   ALFALFA. 

The  soil  for  alfalfa  should  be  well  drained  and  it  should  con- 
tain a  good  supply  of  the  mineral  elements  of  plant  food  in  avail- 
able form.  On  most  soils  in  the  state  moderate  applications  of 
lime  (400  to  800  pounds  per  acre)  will  undoubtedly  prove  profita- 
ble, and  on  some  soils  phosphates  could  be  applied  with  profit. 
The  ground  should  be  prepared  at  least  as  well  as  for  corn.  April 
is  probably  the  best  month  to  sow  alfalfa  in  Illinois,  but  May  is 
also  a  good  time,  and  under  favorable  conditions  good  stands  may 
be  secured  from  Jun?,  July,  or  even  August  seeding,  but  the  late 
seedings  are  more  liable  to  be  injured  by  drouth  and  by  freezing 
during  the  first  winter.  The  seed  should  be  sowed  broadcast  at 
the  rate  of  about  20  pounds  per  acre  and  covered  about  one-half 
inch  deep  by  a  light  harrow.  It  usually  produces  a  good  stand 
when  seeded  with  light  nurse  crops,  as  beardless  barley,  or  a  thin 
seeding  of  oats,  which,  for  the  sake  of  the  alfalfa,  had  better  be 
cut  early  for  oat  hay.  The  more  common  practice,  however,  is  to 
sow  alfalfa  without  a  nurse  crop. 

Two  rules  may  be  laid  down  for  cutting  alfalfa.  For  the  first 
season  the  rule  is,  cut,  or  clip,  alfalfa  whenever  it  seems  to  stop 
growing  vigorously,  and  this  is  to  be  done  regardless  of  the  size  of 
the  plants.  If  the  plants  are  so  small  or  the  field  has  become  so 
weedy  that  the  crop  is  not  worth  taking  care  of,  then  clip  it  with 
the  mower  and  let  the  clippings  lie  on  the  ground.  In  no  case 
should  the  weeds  be  allowed  to  produce  seed.  The  first  rule  then 
is,  whenever  alfalfa  practically  stops  growing,  cut  it.  It  will  then 
spring  up  from  the  rootstock  with  renewed  vigor  and  in  a  few 
weeks  make  a  larger  growth  than  if  it  had  not  been  cut  at  all. 

The  second  rule  applies  to  the  second  and  subsequent  seasons 
and  is  as  follows  :  Cut  alfalfa  hay  when  about  one-tenth  of  the 
heads  are  in  bloom.  This  is  a  rule  commonly  followed  by  exper- 
ienced and  successful  growers  of  alfalfa  in  the  West,  and  it  should 
be  practiced  even  though  the  crop  is  a  light  one,  because  much 
more  would  be  lost  in  subsequent  crops  than  would  be  gained  in 
the  first  one  by  allowing  the  alfalfa  to  reach  full  bloom  before  cut- 
ting. It  should  not  be  cut  very  close  in  the  fall  because  of  danger 
from  winter  killing. 

In  Northern  Illinois  three  to  four  crops  of  alfalfa  hay  can  be 
cut  in  a  good  season ;  in  Southern  Illinois,  five  crops  may  some- 
times be  cut. 

It  is  not  the  purpose  of  this  bulletin  to  discuss  the  value  of 
alfalfa.  It  is  undoubtedly  the  most  profitable  forage  crop  which 
grows,  and  it  not  only  produces  very  profitable  yields  of  most  ex- 


348.  BULLETIN  NO.  76.  [July, 

cellent  hay  and  makes  splendid  pasture,  but  it  is  also  very  effective 
as  a  soil  restorer,  because  of  its  deep  rooting-  system  and  its  power 
(when  supplied  with  proper  bacteria)  to  secure  large  quantities  of 
the  valuable  element,  nitrogen,  from  the  free  and  inexhaustible 
supply  of  the  atmosphere. 

Alfalfa  hay  is  cured  and  harvested  in  about  the  same  manner 
as  red  clover.  It  must  not  be  allowed  to  lie  in  the  swath  until  it 
becomes  thoroughly  dry  ;  or  the  leaves,  the  most  valuable  part  of 
the  hay,  will  be  broken  off  and  lost  in  the  handling-.  The  partly 
cured  hay  is  put  in  small  piles  and  then  allowed  to  dry  out  more 
completely  before  hauling-. 

Alfalfa  hay  and  pasture  tend  to  produce  bloat  in  animals  even 
more  than  red  clover,  and  consequently  it  must  be  fed  with  some 
care. 

SUMMARY  OF  BULLETIN  NO.  76. 

The  past  experience  of  many  farmers  and  the  past  experiments 
of  investigators  have  in  nearly  all  cases  shown  that  alfalfa  is  not 
a  successful  crop  on  Illinois  soil. 

The  experiments  and  observations  described  in  this  bulletin 
establish  the  following-  facts: 

1.  Alfalfa  bacteria  are  usually  not  present  in  Illinois  soil, 
and,  consequently,  the  alfalfa  is  not  able  to  obtain  nitrogen  from 
the  atmosphere  (which  it  would  be  able  to  do  by  means  of  the 
proper  bacteria)  but  it  is  entirely  dependent  upon  the  soil  for  its 
supply  of  this  most  valuable  and  important  element  of  plant  food. 

2.  To  produce  good  crops  of  alfalfa  without  the   "  nitrogen 
gathering  "  bacteria  requires  exceedingly  rich  soil   and  liberal  ap- 
plications of  barnyard  manure  or  other  nitrogenous  fertilizer.     (It 
may  be  observed  that  these  are  the  conditions  of  soil  and  treat- 
ment recommended  for  alfalfa  by  most  writers  in  the  agricultural 
press  of  Illinois  and  other  central  states). 

3.  Even  the  rich   black  prairie  soil  of  Illinois  does  not  fur- 
nish sufficient  available  nitrogen  for  maximum  crops   of   alfalfa. 
(No  other  crop  grown  in  Illinois  requires  such  large  quantitities  of 
nitrogen  as  alfalfa). 

4.  Applications  of  available  nitrogen  to  Illinois  soil  produce 
crops  of  alfalfa  which  yield  from  two  to  four  times  as  much  hay  as 
crops  which  obtain  all  of  their  nitrogen  from  the  natural  supply  of 
the  soil. 

5.  The  inoculation  of  Illinois  soil  with  the  proper  alfalfa  bac- 
teria enables  the  alfalfa  to  feed  upon  the  inexhaustible  supply  of 
free  nitrogen  in  the  air  and  the  inoculated  soil  produces  just  as 


1902.]  ALFALFA  ON  ILLINOIS  SOIL.  349 

large  crops  of  alfalfa  as  soil  which  has  been  heavily'fertilized  with 
commercial  nitrogen.  (Nitrogen  costs  about  15  cents  a  pound  in 
commercial  fertilizers,  and  about  50  pounds  of  nitrogen  are  required 
to  produce  one  ton  of  alfalfa  hay  and  the  ^veight  of  the  free  nitrogen 
in  the  atmosphere  is  equal  to  about  12  pounds  to  each  square  inch  of 
the  surface  of  the  earth}. 

6.  On  most  Illinois  soils,  excepting  limestone  soils,  applica- 
tions of  air-slacked  lime  as  well  as  inoculation  with  bacteria,  will 
be  advantageous  to  the  alfalfa  and  profitable  to  the  farmer.    (Most 
cultivated  soils  are  more  or  less  acid  ;  the  lime  corrects  the  acidity 
and  promotes  the  development  and  activities  of  the  bacteria,  thus 
enabling   the   alfalfa    to   secure   larger   supplies    of    atmospheric 
nitrogen). 

7.  On  some  types  of  soil,  probably  phosphorus  can  be  applied 
with  profit,  for  the  production  of  alfalfa. 

8.  Several  places  have  been  found  in  Illinois  where  the  soil 
is  already  infected  with  alfalfa  bacteria  ;  and,  wherever  the  bac- 
teria have  been  found,  alfalfa  is  being  grown  successfully.     (The 
infected  soil  which  has  been  found  has  usually  been  in  river  bot- 
toms, but  this  has  not  been  the  case  in  all  instances.     Fields  of  in- 
fected soil  have  been  found  in  the  extreme  northern,  in  the  central, 
and  in  the  southern  part  of  the  state,  showing  that,  while  the  al- 
falfa bacteria  are  by  no  means  common  in  Illinois  soil,   they  do 
exist  in  abundance  in  several  widely  separated  sections). 

9.  Alfalfa  bacteria  have  been  introduced   on  the  University 
farm  at  Urbana  and  alfalfa  fields  have  been  seeded  and  inoculated 
by  the  Experiment  Station  in  about  twenty-five  different  places  in 

the  state. 

10.  The  Experiment  Station  advises  farmers  generally,  in  all 

sections  of  the  state,  to  try  to  grow  a  few  acres  of  alfalfa  of  which 
a  small  plot  at  least  should  be  given  the  most  favorable  conditions 
for  success,  by  applying  infected  soil,  and,  if  needed,  lime,  phos- 
phorus, or  potassium. 


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